1. Researchers conducted experiments using a wearable haptic device with multiple vibrators to test whether apparent motion could be used to create a feeling of presence without another person actually being there. 2. Initial experiments tested different membrane thicknesses and vibrator positions to determine optimal parameters for acuity, noise, and pleasantness. 3. Further experiments tested for apparent motion at different body locations but found large variances in vibration amplitudes between subjects, suggesting apparent motion parameters may need to be personalized rather than using standardized values.

1. Figure 1 (on the right). Schematic of the vibrator prototype (to the arrow’s right) with the
functionality of the Master-Slave system (to the arrow’s left) (Adapted from Blanke et. al. Current
Biology. 2014).
The sensation that somebody is nearby when in fact there is no one present is known as a
feeling of presence (FoP).1 Although described by various neurological patients, prior
studies of a FoP have been restricted to only certain environments by a large Master-Slave
machine.1 One solution is a wearable haptic device using apparent motion, the illusion of
motion among standstill objects, to create a FoP. 2 For haptic vibrators utilizing apparent
motion to be used in the creation of FoPs, we must first test the existence of ‘objective’
apparent motion parameters sets applicable to all subjects.
Foundations of Wearable Haptics
in Manipulating Bodily Consciousness
Anush Swaminathan1,2, Myeong Seop Song1, Giulio Rognini1, Simone Gallo1, Olaf Blanke1
1 Lab of Cognitive Neuroscience, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland 2 Boston University, Boston, United States
Introduction
Post development of the prototype and software, trials were conducted on 5
Subjects to determine the optimal membrane thickness and vibrator
position based on 3 parameters: acuity, noise, and pleasantness.
Experimental Approach
Figures 3 and 4. Display of the pre-trials on the left. The figure on the right
demonstrates that Total Apparent Movement = DoS + SoA * (no. of vibrators-1).
SoA is Stimulus Onset Asynchrony, and DoS is Duration of Stimulus.
Trials were conducted on 10 subjects using the Fast Parameter Tracking
Method (FPTM) to locate continuous apparent motion during 10
repetitions in the forearms, neck, and back.
Results
Experiment 2: Apparent Movement
Experiment 1: Membrane Optimization
0.
1.2
2.4
3.6
4.8
6.
7.2
8.4
9.6
10.8
12.
1 2 3 4
SlopeMean
Membrane Number
Figure 5 (on left). Pre-Trial
ANOVA Analysis of Amplitude
Slope Mean (a good indicator
of membrane sensitivity) v.
Membrane Number.
Membrane Optimization
According to Analysis of Variances, Membranes 2 and 4 (of
intermediate thickness) significantly influenced membrane acuity.
Membrane 2 subjectively made less noise, and as such was chosen
for the apparent motion trials.
: p < .00833 in 3 v. 4 and 2 v. 3
(with the Bonferroni Correction
Factor α=0.00833)
Apparent Movement
0
20
40
60
80
100
1 2 3 4 5 6
Amplitude
Vibrator Number
A. Neck
Average Amplitudes for
Vibrators
Average SoA
0
20
40
60
80
100
1 2 3 4 5 6
Amplitude
Vibrator Number
B. Back
0
20
40
60
80
100
1 2 3 4 5 6
Amplitude
Vibrator Number
C. ForearmsFigure 6A, 6B, and 6C. Average Vibrator
Amplitude and Average SoA v. Membrane
Number for the Neck, Back, and the Forearms.
Large variance among vibrator amplitudes
points against a defined cluster of standard
parameters. Non-Normal distributions of
cumulative vibration amplitudes also support
the evidence.
Conclusions and Future Directions
0
10
20
30
40
50
60
70
80
90
0 To 10 10 To 20 20 To 30 30 To 40 40 To 50 50 To 60 60 To 70 70 To 80 80 To 90 90 and over
Count
Distribution of Cumulative Vibration Amplitudes in the Neck
Figure 7. Display of the sample distribution of vibration amplitudes across the
neck.
The large variance among vibration amplitudes lends evidence towards
the personalization of apparent motion parameters by subject. To
further verify the existence of an objective database parameters for
apparent motion, parameters from this dataset can be used in trials to
ascertain whether inputting the same datasets provide different subjects
with the illusion of apparent motion. Once it is verified whether
apparent motion parameters must be personalized by subject, further
research into the fine-tuning of apparent motion and its interaction
with wearable haptics to yield FoPs can be conducted.
Acknowledgements
I would like to thank the Blanke Lab of Cognitive Neuroscience, my Postdoctoral
supervisors and PhD mentor, ThinkSwiss, and the EPFL for giving me the
opportunity to take part in, sponsoring, and organizing the Summer Research
program.
References
1 Blanke et. al. Current Biology. 2014 Nov 17; 24(22):268-6.
2 Oka et. al. Open journal of Molecular and Integrative Physiology. 2011 August.